KR900003249B1 - Semiconductor wafer bonding method and structure thereof - Google Patents

Abstract

Semiconductor wafers are bonded by projecting a central portion of a mirror surface of at least one wafer; opposing the two wafers and bringing their central portion mirror surfaces into contact; and enlarging the contact region from the centre out to the peripheries. The mirror surface of one wafer is projected conically towards the flattened mirror surface of the other.

Description

Bonding method of semiconductor wafer and bonding apparatus thereof

1 is a perspective view excluding some of the bonding apparatus according to the present invention.

2 is a cross-sectional view showing an arrangement state before a joining process in a joining apparatus.

3 is a cross-sectional view showing a bonding apparatus immediately before the bonding step.

4 is a cross-sectional view showing a bonding apparatus in the bonding process.

5 to 7 are sectional views of principal parts showing the bonding process.

* Explanation of symbols for main parts of the drawings

1: Mounting Table 2: Cleaner

3: hermetic phase 4: monitor

5: Remote control unit 6: Bracket for rotating arm

7: X-Y table 8: ITV camera

10: Bonding mechanism of semiconductor wafer 11: Pulse motor for driving θ-axis

12: Z-axis pulse motor 13, 22: hollow shaft

14, 15: screw mechanism 16, 23: drive mechanism

17: support portion 18, 25: holding mechanism of semiconductor wafer

19, 26: flat part 20, 27: through hole

22: rotating arm 28: tool

29: inclined portion 30: contact detection mechanism

31: insulation 32: spring

51: rubber

The present invention relates to a method of joining a semiconductor wafer and a joining apparatus for arranging mirror surfaces formed on a surface of a semiconductor wafer to face each other in a clean air atmosphere, and then bonding the mirror surfaces to one body.

When manufacturing a semiconductor device, a technique of forming a semiconductor layer having a specific conductivity type on a single crystal semiconductor substrate by a vapor phase growth method and then forming a functional element therein is widely used. In such a vapor phase growth method, a semiconductor substrate is used. In order to avoid the incorporation of the impurity layer diffused outward from the outside, various studies have been conducted and many patents have been applied.

As described above, in the case of forming a semiconductor layer having a different impurity concentration by using the vapor phase growth method, it is difficult to precisely adjust the surface impurity concentration and it is difficult to thicken the thickness of the semiconductor layer because of the deposition method.

On the other hand, the recent semiconductor market demand is required for devices with high breakdown voltage, and from this point of view, the vapor phase growth method cannot necessarily be said to be a satisfactory technology.

However, Japanese Patent Publication No. 49-26455 discloses a technique for joining a plurality of semiconductor wafers, that is, a silicon wafer polished with a mirror surface is arranged in an atmosphere filled with oxygen and nitrogen gas. In each mirror surface, phosphorus was diffused using phosphorus phosphate as an impurity source for 30 minutes at a temperature of 1200 ° C., and the silicon wafer thus diffused was heated to a temperature of 1150 ° C. for 1 hour, and then the surroundings were vacuumed. Is pressed at a temperature of 1300 ° C. while applying a pressure of 150 kg / cm ₂ . In this way, the silicon wafer can be pasted through a high concentration of impurity layer, so that the melting point is lowered compared to the method of compressing the semiconductor wafer with a glass layer sandwiched therebetween by applying a pressure at a high temperature. This is a remarkable technology because it can prevent the silicon wafer from partially dissolving.

In the technique disclosed in Japanese Patent Laid-Open No. 49-26455, impurities are diffused at a temperature of 1200 ° C. on a mirror surface of a polished semiconductor wafer, and then pressed at a temperature of 1300 ° C. for both sides. It is supposed to work on a mirror surface.

The fact that the temperature at the time of pressing is higher than the temperature of the diffusion process is expected to diffuse diffusion impurities again, and as a result, the surface concentration of the impurity layer is inevitably forced.

In addition, it is very difficult for the semiconductor wafer to be aligned, and it is very difficult to realize it in a vacuum state, and even if it is possible, the device is very expensive, and the price of the bonded wafer becomes expensive. It became.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of joining a semiconductor wafer and a joining apparatus, which enable the semiconductor wafer to be accurately bonded in a simple manner.

The technology to polish the mirror surface obtained by polishing the surface of the semiconductor wafer with water and then dewatering to remove excess moisture and then to adhere the adsorbed moisture to the mirror surface of the semiconductor wafer in a clean atmosphere is applied to Japan by the applicant. In addition, in the mirror-joining of the semiconductor wafer, the use of a tool capable of forming one surface of the semiconductor wafer in the shape of a wafer allows for a good quality bonding, which has already been filed in Japan by the present applicant. .

However, in such a joining technique, in order to prevent voids from occurring at the interface, not only bubbles are crawled, but also a clean atmosphere is required so that dust does not accumulate. Only when pressure is added uniformly will the effect. By the way, in the automation of the manufacturing apparatus, in which it is necessary to convey or hold the semiconductor wafer, the edge of the wafer is avoided by making the wafer end surface a conveyed portion.

In the method of the present invention, the mirror surface is kept in a reduced pressure state in order to prevent the generation of fine particles due to the debris and the like of the semiconductor wafer being opened, and the semiconductor wafer mirror surfaces are adjusted in a reduced pressure state after adjusting the positions of both surfaces of the semiconductor wafer in order to add an even pressure to the contact surface. Had adopted a way to turn it off.

An apparatus for realizing the above-described method should be installed in a clean atmosphere. Specifically, a pair of hollow shafts are disposed to face each other in the vertical direction, and a moving distance adjusting device is provided below the hollow shaft. Let it be. In this case, the mirror surfaces of the semiconductor wafers are faced to each other by using a mechanism disposed at the end of the hollow shaft to hold the semiconductor wafer, and the driving mechanism is provided while the driving mechanism is installed on the hollow shaft to move them. The support portion fixed is installed so that only the hollow shaft is moved, and the support portion does not move. At the end of the hollow shaft, a semiconductor wafer holding mechanism is installed and the mirror surface of the semiconductor wafer is held therein to determine when the two mirror surfaces are in contact with each other, and a contact sensing mechanism is installed. It is formed of an insulating part fixed to one side of the hollow shaft to be moved with the support, which is to be applied to some pressure.

For example, when the spring is installed between the support and the insulator, the hollow shaft of the upper side is moved as well as the insulator in order to move the hollow shaft located below and to contact the mirror surfaces of both semiconductor wafers. The contact sensing mechanism is operated.

In addition, the support portion, which is not moving, is applied to a mirror surface of the semiconductor wafer which is applied to a holding mechanism of the wafer again by applying a pressure higher than a certain pressure. The end of the holding mechanism of the semiconductor wafer is a material that can be followed as the pressure changes, and a flat portion is provided along the mirror surface of the semiconductor wafer and a plurality of through holes penetrates the semiconductor wafer. Therefore, the holding mechanism can be provided with a tool, and the tool portion facing the flat portion is formed with an inclined portion protruding the central portion thereof. In addition, since the hollow shaft is connected to the pressure reducing mechanism and the hole is also formed to flow in the pressure reducing mechanism, the mirror surface of the semiconductor wafer is caught by the flat portion and can fall off upon decompression. Therefore, the adjustment mechanism of the movement distance is not only capable of adjusting the X, Y, Z axis and angle, but also allows complex adjustment.

Hereinafter, the present invention will be described in detail with reference to the embodiments illustrated in FIGS. 1 to 4.

Although the present invention will be described with respect to a bonding apparatus that can realize a bonding method, it is also an object of the invention to be able to automate a subtle bonding method.

In other words, according to the bonding apparatus of the present invention, as shown in FIG. 1, a cleaning device 2 and a hermetic phase 3 in contact with the mounting table 1 are installed, and a monitor 4 and a remote control unit 5 are installed therein. ), The bracket for rotation arm 6 and the X-Y table 7 are arranged, and the ITV camera 8 is installed at a position of 500 mm from the top surface of the closed phase 3.

Since the cleaning device 2 is installed on the rear surface of the closed phase 3, it is possible to avoid the accumulation of dust on the mirror surface of the semiconductor wafer as compared with the so-called downslow cleaning, and the degree of cleanliness of the first grade or less Is obtained.

Wherein the bonding mechanism 10 of the semiconductor wafer is composed of a portion (A) installed on the X-Y stage and the other portion (B) provided on the rotating arm bracket (6) as shown in FIG. The other part (B) fixed to the bracket (6) is rotated and laminated on the part (A) installed on the X-Y stage to bond the mirror surface of the semiconductor wafer.

The rotating arm bracket 6 corresponds to the hollow shaft 22 and the supporting pillar thereof shown in FIG. 2, and the X-Y table 7 corresponds to the X-Y stage shown in FIG. Will be.

FIG. 2 is a cross-sectional view showing a state in which the A and B portions are not integrated, and FIG. 3 is a cross-sectional view showing a state in which the other portion B is rotated to be fixed a little away from the portion A, and FIG. 4 is It is sectional drawing which shows the process of integrating part A and another part B, ie, the joining process.

The moving distance adjusting mechanism 7 described in FIG. 1 includes an X-Y table, a pulse motor, a screw mechanism, and a flange.

The pulse motor for driving each axis is mounted on the X-Y table, and the θ-axis driving pulse motor 11 and the Z-axis driving pulse motor 12 are stacked on the Y-axis moving plate. do.

Specifically, the nut and screw are attached to the hollow shaft 13 arranged in the vertical direction, and the screw mechanisms 14 and 15 are respectively installed in the pulse motors 11 and 12.

In addition, the hollow shaft 13 is filtered along the drive unit 17 by filtering the drive mechanism 16 assembled with the linear ball bearing to move in the vertical direction. Accordingly, the support unit 17 integrates the θ-axis driving pulse motor 11, the Z-axis driving pulse motor 12, and the screw mechanisms 14 and 15.

Therefore, the screw mechanism 14 is operated by the θ-axis driving pulse motor 11 so that the semiconductor wafer installed in the portion A rotates about the θ axis, and the Z-axis driving pulse motor 12 is rotated. As a result, the screw mechanism 14 becomes a lead screw, so that the semiconductor wafer installed in the A portion is raised or lowered in the Z direction.

Therefore, the semiconductor wafer is moved back, front, left, and right by the X-Y table 7, and the amount of movement in the Z direction is such that the screw mechanism 14 does not come out.

On the other hand, one end of the hollow shaft 13 is connected to a decompression mechanism (not shown, only arrows) while the other end is connected to the semiconductor wafer noise mechanism 18.

The upper end of the catching mechanism 18 is made of, for example, a rubber material that follows the pressure change, and forms a flat portion 19 in a direction perpendicular to the vertical direction, and the flat portion 19 thereon. A plurality of through-holes 20 penetrating through the plurality of through holes 20 are provided so as to allow the pressure reducing mechanism to flow thereon so as to hold the mirror surface of the semiconductor wafer loaded on the flat portion 19.

The catching mechanism 18 may be provided with a tool for protruding the mirror surface center of the semiconductor wafer. The tool protrudes the center of the portion facing the flat portion 19 so as to protrude the inclined portion at the end thereof. By forming it, it arrange | positions so that the flow of the said pressure reduction mechanism and a through hole may not be disturbed.

On the other hand, the portion B is fixed to the rotating arm 22 installed to rotate the bracket 6 for the arm. From this, a pair of hollow shafts 22 are arranged on the hollow shafts 13 so that the driving mechanism 23 is hooked so as to be movable in the vertical direction so as to be fixed by the support 24 to be integrated. Here, the drive mechanism 23 linear ball bearings are assembled and formed. Further, at one end of the hollow shaft 22, a semiconductor wafer holding mechanism 25 is provided so that the semiconductor wafer mirror surface held by the holding mechanism 18 can be joined.

Therefore, the structure 25 is the same as the catching mechanism 18, and the flat part 26 and the some through-hole 27 are formed, and the tool 28 is provided, but this tool 28 As described above, the inclined portion 29 is formed.

The other end of the hollow shaft 22 is connected to a decompression mechanism (not shown, only arrows) so that it can be passed through the through hole 27.

In the present embodiment, the contact sensing mechanism 30 is provided in the B portion, but the so-called contact sensor in which the movable parts fall during contact is used here. That is, the contact sensing mechanism 30 has the support portion 24 and the insulation portion 31 by fixing the ring-shaped insulation portion 31 to the hollow shaft 22 adjacent to the drive mechanism 23. To form.

As shown in FIG. 3, as the hollow shaft 22 moves, the spring 32 is hung between the insulating layers 31 so as to apply pressure to the floating support 24 fixed thereto. At the same time as the component falls, an extra pressure is applied to the spring end caught in the support portion, so that pressure is transferred to the mirror surface of the semiconductor wafer.

As the touch sensing mechanism, in addition to the above-described structure, there are devices similar to those in which the stress is detected in accordance with the contact, but any of them can be applied, and the place of implementation thereof is not recognized in the above description.

Next, the operation of the bonding apparatus will be described.

With the switch of the remote control unit 5 shown in FIG. 1 being turned on, the pressure reducing mechanisms of the A and B sections are operated so that the mirror surface of the semiconductor wafer is held on the flat portion, and then the rotating arm 22 is rotated. As shown in FIGS. 3 and 5, the portion B is stopped about 1 mm from the portion A. FIG. At this time, the holding of the semiconductor wafer, for example, when the wafer radius is 100 mm, the heat is set to 300 mm as the radius of curvature.

Subsequently, the screen of the monitor 4 captured by the IVT camera 8 can be viewed, so that the semiconductor wafer is aligned according to various direction operation switches of the remote control unit 5. In addition, the operation is performed by the pulse motors 11 and 12 to adjust the X, Y, and θ axes, and then move to the Z axis rise in the next step after confirming the completion.

The precision of this operation is 0.5 mm in the X and Y axes, and θ is 0.9.

According to the ITV camera 8, the above-described positioning is performed by injecting two points of the tip of the orbiter portion of the mirror surface of the semiconductor wafer and three points of the point perpendicular to the orbiter portion to the monitor 4 to display the image. As it can be seen, it can be operated according to the control switch of various directions.

The degree of elevation in the Z-axis direction, when the lower semiconductor wafer is brought into contact with the upper surface of the semiconductor wafer by the switch of the remote control unit 5, the components of the contact sensing mechanism 30 falls, and the hollow shaft 13 in the signal Since the moving distance of) is measured, it manages the load of the joint pressure as it rises to an arbitrary setting position.

If the hollow shaft 13 is different at the set position, the pressure reducing mechanism is released and at the same time, the Z axis, that is, the hollow shaft 13 is stopped, and then is lowered to return to the origin.

The rotary arm 22 then rotates in reverse to return to origin, and then takes out the semiconductor wafer to be bonded.

Next, a method of bonding a semiconductor wafer will be described with reference to FIGS. 5 to 7.

As a pretreatment prior to the joining process, mirror polishing, washing and washing are performed. Two semiconductor wafers are prepared, and the surface to be bonded is mirror polished to form a roughness of the surface of 500 kPa or less.

At this time, according to the surface state of the semiconductor wafer, degreasing and stain film deposited on the surface of the semiconductor wafer are continuously removed by H ₂ O ₂ + H ₂ SO ₄ ? HF? Dilution HF treatment.

Subsequently, the semiconductor wafer mirror surface is washed with clean water for a few minutes and then dehydrated such as spinner treatment before room temperature.

Since the treatment process removes the excess water that is expected to be adsorbed on the mirror surface of the semiconductor wafer, it is possible to avoid heating and drying at 100 ° C. or more in which the absorption water is almost diffused.

In this process, the semiconductor wafer is bonded by the joining mechanism in a clean atmosphere of 1st class or less. As described above, after the semiconductor wafer is disposed in the flat portion of the catching mechanism, the semiconductor wafer mirror surface can be maintained in accordance with the operation of the decompression mechanism. do.

As shown in FIG. 5, the center of the semiconductor mirror surface is protruded according to the reduced pressure (for example, 10 ² torr) through the elastic force of the rubber 51 constituting the inclined surface of the tool and the hard part and the drilled hole. In addition, although the other semiconductor wafer mirror surface is maintained on the flat part of one hollow shaft 13 on the same principle, there may be a case where the center part is flattened as described above. In this case, the alignment is first performed by maintaining the distance between the two peninsula wafers at a distance of about 1 mm.

Subsequently, as shown in FIGS. 6 and 7, as shown in FIGS. 6 and 7, the lower stage is raised to contact only the center portion, and the upper and lower Vacs are simultaneously released to contact the entire semiconductor wafer.

By performing such a bonding process, both semiconductor wafers are integrated and a composite semiconductor wafer can be obtained. In the bonding process, the contact pressure is equalized by the operation of the contact sensing mechanism, and the deactivation of the pressure reducing mechanism is performed. It can be joined toward the periphery from the mirror central portion.

As described above, the joining process of the present invention can prevent the occurrence of gaps, and according to the method of the present invention, the mirror surface center portions of both semiconductor wafers are aligned, and then the joining is performed from the center portion toward the periphery. In addition, when the mirror surfaces of both semiconductor wafers protrude, the gas is prevented from being rolled up by the alignment, and the pressure at the time of contact is made uniform according to the presence of the contact sensing mechanism, so that the occurrence of gaps can be reduced. Therefore, there is an advantage that can improve the product ratio for the raw material of the composite semiconductor wafer.

Claims (2)

1. A method of bonding a semiconductor wafer to mirror a silicon wafer by mirror polishing, wherein the mirror surfaces formed on the semiconductor wafer are disposed to face each other in a clean atmosphere, and the steps of maintaining the mirror surfaces of the semiconductor wafers facing each other under reduced pressure. And deforming at least one side of the mirror surface of the semiconductor wafer such that its central portion protrudes, detecting a central portion contact of the mirror surface of the semiconductor wafer, and releasing a reduced pressure state of the mirror surface of the semiconductor wafer. Bonding method of a semiconductor wafer. 1. A method of bonding a semiconductor wafer to mirror silicon wafers by mirror polishing, the method comprising: first and second hollow shafts disposed in a clean atmosphere and installed to face each other in a vertical direction, and a decompression mechanism connected to both hollow shafts, the first And a wafer holding mechanism connected to the second hollow shaft, a flat portion formed of a material that changes according to the pressure change of the holding mechanism, and the flat portion passing through the first and second hollow shafts. And a through hole formed by at least one of the holding mechanisms, an inclined portion formed by protruding a central portion of the tool portion so as to face the flat portion, and being driven so as to be caught by the first and second hollow shafts. A contact sensing mechanism that is caught by any one of a mechanism, a support for fixing the drive mechanism, and the first and second hollow shafts. And a moving distance adjusting mechanism that is caught by the second hollow shaft.

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